1. Field of the Invention
The following description relates to an organic light emitting display device and a driving method for the same.
2. Discussion of Related Art
Recently, various flat panel display devices that are lighter in weight and smaller in volume, as compared with a cathode ray tube display device, have been developed. Among these flat panel display devices, there are a liquid crystal display device, a field emission display device, a plasma display panel display device, and an organic light emitting display device, etc.
The organic light emitting display device displays an image using organic light emitting diodes OLED that generate light by recombination of an electron and a hole.
The organic light emitting display device as described above has a high viewing angle, excellent color representation, thin thickness, etc., so that its application field has been expanded to PDAs, MP3s, etc., besides cellular phones.
FIG. 1 is a schematic circuit view showing a pixel adopted for an organic light emitting display device. Referring to FIG. 1, the pixel includes a first transistor M1, a second transistor M2, a capacitor Cst, and an organic light emitting diode OLED.
The source of the first transistor M1 is coupled to a first power supply ELVDD, the drain of the first transistor M1 is coupled to the anode electrode of the organic light emitting diode OLED, and the gate electrode of the first transistor M1 is coupled to a first node N1. In addition, the first transistor M1 allows driving current to be flowed from the source to the drain corresponding to the voltage of the first node N1.
The source of the second transistor M2 is coupled to a data line Dm, the drain of the second transistor M2 is coupled to the first node N1, and the gate electrode of the second transistor M2 is coupled to a scan line Sn. In addition, the second transistor M2 allows a data signal flowing on the data line Dm corresponding to a scan signal transferred through the scan line Sn to be transferred to the first node N1.
The first electrode of the capacitor Cst is coupled to the first power supply ELVDD, and the second electrode of the capacitor Cst is coupled to the first node N1 so that it allows the voltage of the first node N1 to be maintained even though the electrical coupling between the data line Dm and the first node N1 is blocked by the second transistor M2.
The organic light emitting diode OLED includes an anode electrode, a cathode electrode and an emission layer therebetween and light-emits light on the emission layer corresponding to the magnitude of the driving current that flows from the anode electrode to the cathode electrode. The cathode electrode is coupled to the second power supply ELVSS whose voltage is lower than that of the first power supply so that the current can be flowed from the anode electrode to the cathode electrode.
The pixel formed as described above light-emits light by receiving a first power (e.g., a voltage) of the first power supply ELVDD and a second power (e.g., a voltage) of the second power supply ELVSS from an external power source, such as a battery. In a portable device that receives and uses power from a battery such as a cellular phone and a PDA, etc., it is important to extend a battery use time.